A combination of microstructural characterization, experimental measurements, and computational procedures has been applied to quantify the thermal conductivity of FRMs as a function of temperature. A simple device for experimentally measuring effective thermal conductivities, based on a slug calorimeter, has been presented. For these dynamic reactive materials, exposing the FRMs to multiple heating/cooling cycles provides valuable information on the endothermic and exothermic contributions of reactions, phase changes, and mass transfer of (hot) gases to the effective thermal conductivity. Quantifying the porosity and pore size of these materials provides valuable inputs for estimating their thermal conductivity over a wide range of temperatures. Porosity can be assessed by measurements of the bulk and powder densities of the materials, while pore size can be assessed using optical microscopy or x-ray microtomography. The results support the view that reducing the pore size in these materials is a viable approach to reducing their effective thermal conductivity. As the linkages between microstructure and thermal properties are explored further, the knowledge base developed should lead to new and improved FRMs, as well as aiding in the optimization of the thermal performance of existing materials.